The present invention concerns a novel grid parabolic antenna which is constructed in a manner for reducing the amount of back radiation.
In U.S. Pat. No. 2,850,735, a grid parabolic antenna is disclosed in which a number of spaced parallel aluminum tubular reflector ribs are contoured and their ends are connected to a peripheral hoop to form a parabolic antenna structure. A primary advantage of the grid type parabolic antenna over a solid parabolic antenna is that the grid antenna has wind loading characteristics of only 20 percent to 40 percent of comparable size solid parabolas.
Both grid type parabolic antennas and solid parabolic antennas have leakage around the antenna thereby resulting in a certain amount of side and back radiation. During transmission, the side and back radiation may cause interference with other signals which are being fed in the same direction from other antennas. It has been found that prior art grid antennas, such as illustrated in U.S. Pat. No. 2,850,735, have substantially more back radiation than solid antennas. However, the low wind loading characteristics of the grid antennas makes the use of the grid antennas necessary under many conditions.
FCC Part 94 includes a category A requirement which specifies a maximum amount of side and back radiation that is permitted with respect to parabolic antennas. In the 2100-2300 megahertz band, a conventional six-foot solid parabolic antenna complies with the category A requirement, but the conventional six-foot grid type parabolic antenna does not comply with the category A requirement. Therefore, it has been believed that a six-foot grid type parabolic antenna could not be used in the 2100-2300 megahertz band where FCC Part 94 category A is applicable. However, I have discovered a novel construction for reducing significantly the back radiation of a grid antenna.
Therefore, it is an object of the present invention to provide a grid antenna having less wind resistance than a solid antenna but also having less back radiation than the back radiation provided by prior art grid antennas.
A further object of the present invention is to provide a grid antenna which has substantially no more back radiation than the back radiation of a solid antenna of the same size.
Another object of the present invention is to provide a grid antenna that has reduced back radiation and that is relatively simple in construction and relatively easy to manufacture.
Other objects and advantages of the present invention will become apparent as the description proceeds.